Batteries - TEST SETUP

1. USEFUL CAPACITY.

What USEFUL means for us?
Total capacity of batteries (e.g. 3000 mAh) is usually determined in the most favorable conditions. Favorable for the producer, of course :-). So, for example, with a low current load (1 A) - the voltage drop on the internal resistance of cell is then minimal and the battery works longer than in our mods (which need a higher current, often much higher). Another issue is the cut-off voltage, which the manufacturers often set at 2.5 V. Our mods typically cut-off around 3-3,3 V. So the usable capacity for us will always be less than declared by the manufacturer. And how to designate it? Simply by vaping and measuring the energy consumed. Some mods allow this, I will show it below. 

1.1. 18650 batteries.

The measurements were carried out by use of the SXmini mod (by YiHi). SXmini nicely shows all the electrical parameters and additionally MEASURES the total power taken from battery - below you can see how it looks like in practice:

[Some theory - you can skip this section]
The energy measured by the SX-a is expressed in joules = watts * seconds [1J = 1W * 1s]. So dividing it by 3600 we get the result in Wh, and here it is only a step to Ah - just dividing it by the operating voltage. Well, but what the operating voltage is? It may be accurately calculated by integrating the battery voltage curve but usually a simplification is taken: an average voltage within given range of work. So, because the average cut-off voltage during my tests was 3.3 - 3.4 V and batteries start from 4.2V, I taken the 'halfway' value 3.85V.

For each battery I use the SAME setup (MTL atomizer with ~1 ohm coil at 20 W) and measure:
* cut-off voltage - which means the voltage at the moment when the SXmini third time showed crossed battery mark,
* total energy given by battery until cut-off moment.
Then, on the basis of energy I calculated the useful capacity of each battery.

1.2. 21700/20700 batteries.
In this case I use the Mirage mod with DNA75c chip - it measures the energy taken in Wh:

So all you need to do is divide the energy by average voltage, 3.85 V again.
For each battery I use two setups (each of them is always the same):
a) MTL atomizer with ~1 ohm coil at 20 W,
b) DTL atomizer wit 0,15 ohm coil at 45 W.

So we get two charts as a result.

For reference I also show the result of the LG HG2 battery in the charts.

NOTE: DNA chip has a not so good ;-) performance, so you can easily add 10% of the capacity obtained on it.

1.3. 26650 batteries.

Here I use the HCigar VT75 mod with DNA75 chip and Escribe software. I prepared the Python script which enforces automatic "vaping" according to the scheme:

* 5 s of vaping,
* 10 s break.
As you can see below:

This method is BRILLIANT because (as you can see in the picture) Escribe instantly calculates total energy taken!

For each battery I use the SAME setup: DTL atomizer with ~0.5 ohm coil at 45 W.

NOTE: DNA chip has a not so good ;-) performance, so you can easily add 10% of the capacity obtained on it.

2. CONTINUOUS LOAD.

Continuous load tests were carried out in test setup shown below:

As you can see:
a) battery was placed in charger (of course disconnected, just for hold - charger pins were isolated),
b) as a load was power resistor 0.5 ohm (50W) connected to the battery by switch,
c) to the battery terminals have been connected:
- multimeter (voltmeter),
- thermocouple from thermometer (near minus pin).

Thanks to this we can observed:
- battery voltage,
- minus pin temperature.

In such constructed circuit current may reach ~8A, and resistor is heated to more then 100 *C - so don't do it at home.

After preparation the circuit have been closed and test was carrying out until the battery voltage reached ~3.3V (actually tests stopped at 3.0V but vaping on mechanical mod below 3.3V makes no sens). The entire test have been recorded by use of camera and the movie was used to put the values into the Excel. Below you can see a sample movie with the test of Efest 2100 mAh - I warn you that it is boring :-) In minute 14:15 you can see the temperature of resistor.